1. Field of the Invention
The present invention relates to a pressure-sensitive adhesive tape which comprises a supporting fabric woven of thermoplastic-synthetic-resin-made flat yarn, and a pressure-sensitive adhesive applied to the supporting fabric, which can be cut by-hand in the direction rectangular to the longer direction of the tape, that is, in the warp direction, and which is useful, for example, for sealing packaging materials and for binding construction materials to be cured.
2. Background Art
The use of pressure-sensitive adhesive tapes whose supports are flat-yarn-woven fabrics is extending in the field of packaging including the sealing of packaging materials and the binding of construction materials to be cured. However, the conventional pressure-sensitive adhesive tapes have such an inconvenience that a cutter or the like is needed to cut the tapes. In order to obviate this inconvenience, the tear properties of the tapes in the crosswise direction thereof were improved while the strength of the tapes in the lengthwise direction thereof was maintained high. As a result, it became possible to tear the tapes easily by hand. Thus, the use of the pressure-sensitive adhesive tapes is further extending rapidly.
As means for improving the tear properties of the pressure-sensitive adhesive tapes in the crosswise direction thereof without decreasing the strength of the tapes in the lengthwise direction thereof, the following methods have been proposed so far: a method in which weft yarn whose fineness shown in deniers is lower than that of warp yarn is used, and, at the same time, the thread count of weft yarn is made high (Japanese Patent Laid-Open Publication No. 118483/1986); a method in which a resin having a low heat-softening point and a low crystallinity is incorporated into weft yarn, and the weft yarn is allowed to deteriorate by heat applied thereto during the process of lamination; and a method in which weft yarn having a draw ratio lower than that of warp yarn is used (Japanese Utility Model Publication No. 30362/1975).
It is certain that pressure-sensitive adhesive tapes obtained by the above methods have lowered tear resistance in the crosswise direction of the tapes and that it becomes easier to cut the woven fabric layers of the tapes. However, excellent tear properties cannot be obtained unless the adhesive strength of the thermoplastic resin laminated is sufficiently high. It is therefore necessary to make the lamination layer thick. This is uneconomical, and tapes having thick lamination layers have impaired flexibility.
Further, even when high-pressure low-density polyethylene resins, which are the lowest in rigidity among thermoplastic resins usually used for lamination, are laminated, the resulting tapes are insufficient in flexibility.
An object of the present invention is to provide a pressure-sensitive adhesive tape which is so excellent in tear properties in the crosswise direction that the tape can be easily torn by hand and which is so flexible that the tape can be applied even to curved surfaces or to projected portions.